This application claims the benefit of Korean Application No. 2002-10261, filed Feb. 26, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a photosensitive drum structure for an image forming apparatus using a photosensitive belt, and more particularly, to a photosensitive drum structure for an image forming apparatus used in an electrophotographic printer.
2. Description of the Related Art
In general, an electrophotographic printer such as a laser printer forms a latent electrostatic image on a photosensitive medium, develops the latent electrostatic image with a toner having a predetermined color, and transfers the developed toner image to a printing paper in order to obtain a desired image. The photosensitive medium is typically a photosensitive belt or a photosensitive drum.
FIG. 1 is a view of a portion of an image forming apparatus using a known photosensitive belt as a photosensitive medium. Referring to FIG. 1, the rotation path of a photosensitive belt 10 that travels a continuous path due to rollers 10a, 10b, and 10c includes an eraser 12, a charger 14, a laser scanning unit (LSU) 16, and a plurality of developing units 18a, 18b, 18c, and 18d. The eraser 12 erases charges on the photosensitive belt 10. The charger 14 charges the photosensitive belt 10 with a predetermined electric potential. The LSU 16 radiates light onto the photosensitive belt 10 to form a latent electrostatic image. The plurality of developing units 18a, 18b, 18c, and 18d are disposed in series along the travel direction of the photosensitive belt 10 and each develops the latent electrostatic image as a toner image with a different color. The developed toner image is transferred to a transfer belt 20 that circulates in contact with the photosensitive belt 10.
However, in the above-described transfer method, the photosensitive belt 10 may move laterally outside of a transfer range of the image. Thus, a steering unit (not shown) is needed to adjust the photosensitive belt 10.
FIG. 2 is a view of a portion of an image forming apparatus using a photosensitive drum as a photosensitive medium to solve the problems caused by the use of a photosensitive belt. Elements that are the same as those in FIG. 1 are described with the same numerals, and thus their detailed descriptions are omitted.
Referring to FIG. 2, instead of the photosensitive belt 10 of FIG. 1, a large-sized photosensitive drum 30 is used. A plurality of developing units 28 to develop a latent electrostatic image on the photosensitive drum 30 are disposed along the circumferential surface of the photosensitive drum 30. Developer rollers 28a, 28b, 28c, and 28d are positioned at the tip of each developing unit 28. The developer rollers 28a, 28b, 28c, and 28d contact the photosensitive drum 30 and develop the latent electrostatic image with a toner in the developing units 28 with a developing nip N, having a predetermined width.
However, a different problem occurs in the manufacture of the photosensitive drum 30. That is, if a small-sized photosensitive drum 30 having a diameter of 25-32 mm is manufactured, a small-sized rotary drum having a diameter of 25-32 mm is dipped in a container containing a photosensitive solution to form a photosensitive layer on the surface of the rotary drum. In this case, a plurality of small-sized rotary drums are manufactured at the same time, and thus manufacturing costs are low. However, since the photosensitive drum 30 uses a large-sized rotary drum having a diameter of about 150 mm, it is difficult to dip multiple rotary drums in the container containing the photosensitive solution. Also, it is expensive to manufacture the photosensitive drum 30. Further, since the photosensitive drum 30 is rigid, the developing N must be narrow, and the developing units 28 do not develop the image well.
Accordingly, it is an object of the present invention to provide a photosensitive drum structure for an image forming apparatus in which a gap to provide a cushion between a rotary drum and a photosensitive belt is formed by adhering the photosensitive belt on steps having a predetermined height that are formed at both ends of the circumferential surface of the rotary drum.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing a photosensitive drum for an image forming apparatus, the drum including a cylindrical rotary drum having steps at both ends of a circumferential surface thereof, and a photosensitive belt wound around the rotary drum and attached thereto with an adhesive adhered to the steps, wherein a gap is formed between the circumferential surface of the rotary drum and the photosensitive belt.
According to an aspect of the present invention, the gap is filled with air or an elastic member.